Gas turbine for ship propulsion



Dec. 18 1962 A. MARQUE 3,069,134 GAS TURBINE FOR SHIP PROPULSION Filed Sept. 12, 1958 F IG- 2 i (Fr/or Art) INVENTOR. Andre Marque Afiornegs United States Patent 3,069,134 GAS TURBINE FOR SHIP PROPULSION Andr Marque, Paris, France, assignor to Aktiengesellschaft Brown, Boveri & Cie, Baden, Switzerland, a joint stock company 4 Filed Sept. 12, 1958, Ser. No. 760,800 Claims priority, application France Oct. 1, 1957 2 Claims. (Cl. 253--70) The present invention relatesto propulsion systems and more particularly to propulsion systems for ships wherein the power is transmitted to the propeller shafts by means of gas turbines.

In the use of turbines for driving ships, and particularly the case with steam turbines, it is known to use a relatively large power turbine for propelling the ship in the forward direction, and a separate turbine of relatively smaller power for reverse movement, the two turbines generally being located on the same drive shaft and within the same housing. jA similar arrangement can be employed when the turbines are of the combustion gas type but, in contrast to steam turbines, difficulties are encountered because the reverse turbine cannot be placed under vacuum, when it is driven counter to its normal direction as is the case when the forward turbine is operating. Because of this, there is a power absorption in the reverse turbine that reduces considerably the efliciency of operation when the forward turbine is in use.

Various constructions have been suggested to reduce propulsion of the ship, but such constructions even though they yield a higher efiiciency in the forward direction,

cause a considerable drop in efliciency of operation in the reverse direction which is, of course, undesirable. It is possible to suggest other solutions which yield higher elliciency of operation in both directions but these entail more complicated and hence more expensive constructions.

The object of the present invention is to improve the prior art constructions in a more simple and efficient manner which reduces the undesired interaction between the forward and reverse turbines, each upon the other, when either one of them is operating. This objective is attained in general by improving the direction of flow of the discharge gases from the reverse turbine into the common passageway through which flows the discharge gases from both turbines. In particular, the desired result is obtained by designing the gas discharge passageway from the reverse turbine such that the gases are first subjected to centripetal flow ie they first flow towards the turbine axis and are then turned along acurved path so as to flow in a centrifugal direction which generally coincides with the direction of flow of the discharge gases from the forward turbine in the discharge passageway common to both turbines. By thus designing the gas discharge passageway from the reverse turbine, essentially none of the discharged gases from the reverse turbine, when it is operating, will be able to enter the blading of the forward turbine; conversely, when the forward turbine is operating, essentially none of the gases which it discharges will be able to enter the blading of the reverse turbine.

The foregoing and other objects and advantages inherent in the invention will become more apparent from the following detailed description of several different embodiments thereof and from the appertaining drawings. In these drawings:

FIG.'1 is a'longitudinal view in central vertical section of the interior of a gas turbine constructed in accordance with the present invention;

FIG. 2 is a similar view illustrating a construction known in the prior art;

FIG. 3 is a view similar to FIG. 1 showing a somewhat "ice different embodiment in accordance with the present invention; and

FIG. 4 is also a view similar to FIG. 1 showing yet another embodiment of the invention.

With reference now to FIG. 1, the gas turbine propulsion plant for the ship is seen to comprise a four stage forward turbine 1 for driving the ship ahead and a single stage reverse turbine 2 for driving the ship astern. The stationary blading 1a of the multi-stage forward turbine is secured to the interior wall of the casing 3 and the stationary blading 2a of the single stage reverse turbine 2 is likewise secured to another wall portion of this same casing 3. That is to say, the same'casing is used to house both the forward and reverse turbines. The movable blading 1b of the forward turbine and the movable blading 2b of the reverse turbine are mounted in suitable axially spaced relation on the same shaft 4 which is coupled to the propeller shaft of the ship by reduction gearing, not shown. Combustion gas for driving the forward turbine 1 is introduced to the latter through a passageway 5 and exits through a discharge passageway 6. Combustion gas for driving the reverse turbine 2 is introduced to the latter through passageway 7 and exits through the same passageway 6 as carries the discharged gases from the forward turbine 1; Obviously, when the forward turbine 1 is being driven, the high pressure fluid inlet passageway 7 to the reverse turbine 2 is cut off. :Conversely,

when the reverse turbine 2 is being driven, the high pres-.

sure fluidinlet passageway 5 to the forward turbine 1 is cut off.

As previously explained, a principal object of the present invention is to so design the gas discharge passageways from the forward and reverse turbines, and which are common in part, in such manner that there will be a minimum of undesirable interaction therebetween. One principal structural aspect of the invention concerns the configuration of the gas discharge passageway from the reverse turbine 2. Its design is such that the gases issuing from the movable blading 2b are first subjected to a centripetal motion in the direction of the turbine axis x-x and are. then turned through an angle of substantially so as to flow in a generally centrifugal direction away from such axis. To effect this result it will be seen 0 that turbine shaft 4 is provided with peripheral groove 8 disposed normal to the axis thereof and which has a substantially semi-circular cross section. is located immediately adjacent the gas outlet from the blading 2b of reverse turbine 2, and opposite this groove the turbine casing 3 includes a circular flange like extension 9 which projects radially inward at a steep angle to the turbine'axis and terminates at a point directly oppo sitejand spaced radially outward from the bottommost point of groove 8-. The groove'S in conjunction with the circular extension 9 establishes a circular curved gas exit passageway 10 for the gases leaving blading 2b, the passageway extending through an angle great enough to cause the discharged gases to first fiow in the passageway in a centripetal direction and then turn gradually so as to flow in a centrifugal direction. The exit of passageway 10 joins the discharge passageway 6.

In the prior art construction as exemplified by FIG. 2 where no centripetal motion of the discharge gases is produced, the suction effect of the rotor blading 2b of the reverse turbine on the discharge gases from the forward turbine is considerable when the forward turbine isoperating. .This is due to the fact that when the forwardturbine is being driven, in which event flow of high pressure gaseous fluid to the reverse turbine is cut off, the reverse turbine then acting as a radial compressor creates an excess pressure at the tip ends of the rotor blading of the reverse turbine and a corresponding nega- The groove 8 tive pressure at the root ends of such blading, thus causing a suction effect which draws in part of the discharge gases from the forward turbine, compresses it and then gives it off again to the discharge passageway. This undesired and considerable circulation of the discharge gases from the forward turbine through the blading of the reverse turbine, as indicated by the arrow in FIG. 2 is practically unhindered in that prior art construction because the gases are free to flow unhindered along the surfaces of the support housing for the stationary or guide blading and thus impose a continuous reduction in output during forward motion of the ship. In the improved construction in accordance with FIG. 1, such suction effect is greatly reduced. This is attributable to the presence of the flange like extension 9 which obstructs outflow of gases from the blading tips to the discharge passageway and thus decreases the suction effect at the roots of the blading thus rendering it practically impossible for any of the gases discharged from the forward turbine 1 along the passageway 6 in the direction of the arrow A to enter passageway 10. Thus circulation of the discharge gases from the forward turbine 1 in the blading of the reverse turbine 2 will be reduced to a minimum and the power thus undesirably absorbed will be correspondingly small.

In a similar manner, because the discharge gases from reverse turbine 2 enter the passageway 6 in the direction of arrow B in an essentially centrifugal direction of motion generally coinciding with the direction of flow from forward turbine 1, there is very little possibility of such gases flowing to the right in passageway 6 and entering the blading of the forward turbine 1. Moreover, the cross section of the discharge passageway is such that aerodynamic resistance to flow is reduced to a minimum and the braking effect on the discharge gases from turbine 2 is thus correspondingly small.-

In order to effect a further improvement in operation, the cylindrical portion 4a of the turbine shaft 4 which carries the movable blading 1b of the forward turbine 1 has a diameter which is somewhat less than the shaft diameter at groove 8 and joins the latter by means of a concave curved portion 4b, i.e. the shaft diameter progressively increases between the cylindrical portion 4a and groove 8. Thus the discharge gases from turbine 1 flow along a curved path leading away from the turbine axis, as indicated by arrow A, which tends to keep them away from the mouth of the discharge passageway 10 and thereby makes it even more difficult for these discharge gases to enter passageway 10.

A slightly different embodiment of the invention is illustrated in FIG. 3 wherein it will be seen that the curvilinear discharge passageway 10' for the discharge gases. from the reverse turbine 2 is established by an extension 9', similar to the extension 9 shown in FIG. 1, in conjunction with a cylindrical deflecting member 11 which surrounds the turbine shaft 4' which, in this case, is cylindrical throughout the portion thereof between the forward turbine 1' and the reverse turbine 2. The deflecting member 11 is provided with a peripheral groove 11a opposite the innermost end of the extension 9', this groove being concave in cross section and corresponding in function to the groove 8 in FIG. 1. The cylindrical deflecting member 11 is spaced slightly radially outward from the periphery of turbine shaft 4 and is attached to the extension portion 9' of the turbine casing by means of a plurality of supporting plates 12 which are distributed about the periphery of the extension 9'. In addition to the peripheral groove 11a, the deflecting member 11 is curved concavely at 11b to form a curvilinear wall portion of the gas discharge passageway 6 from the fora ward turbine 1'. This curved wall portion 11b corresponds in function to the curved discharge gas guiding portion 4b of the turbine shaft in the embodiment according to FIG. 1., In this embodiment, thedeflecting member is stationary, but it can also be secured in place on the turbine shaft 4' so as to rotate therewith.

A still different embodiment of the invention is shown in FIG. 4. This embodiment is similar to that of FIG. 3 and hence corresponding components in these views have been given the same reference numerals. It differs from FIG. 3 in that the deflecting member 11 is provided 1 with a peripheral extension 11c which projects outwardly from the turbine axis at an angle, this extension 110 being generally parallel with the extension 9' and spaced therefrom in the discharge passageway 6' so as to form at the outer side thereof a continuation of the diffuser portion of the latter. The inner side of the extension 110 presents an essentially fiat face which is tangent to and forms an outwardly extending continuation of the curve which establishes the groove 11a. The extension 11c in conjunction with the extension 9 enhances the centrifugal channeling movement of the discharge gases from the reverse turbine 2' and moreover reduces the gas discharge losses from the forward turbine 1' when the discharge velocity is very high because of the fact that it extends the diffuser section established by the passageway 6.

In conclusion it will be understood that the foregoing embodiments of the invention which have been described and illustrated are to be considered typical rather than limitative of the various constructions possible and hence permit of various changes in the construction and arrangement of parts without, however, departing from the spirit and scope of the invention as defined in the appended claims. Moreover, the invention is not limited to applications where the reverse turbine is of the single-stage type but can be applied equally as well to installations wherein the reverse turbine is provided with a plurality of stages.

I claim: '1. A gas turbine for ship propulsion comprising a casing, a rotary shaft within said casing, stationary blanding carried by said casing, movable blading carried by said shaft, said stationary blading and said movable blading being cooperatively arranged to form a forward turbine and a reverse turbine axially spaced from each other, a first passageway extending longitudinally along the surface of said shaft in the direction of said reverse turbine and thence radially out of said casing for discharging gases from said forward turbine when said forward turbine only is being driven and a second passageway for discharging gases from said reverse turbine into said first passageway when said reverse turbine only is being driven, said second passageway being constituted in part by a peripheral groove in said shaft of arcuate cross section and normal to the shaft axis and disposed adjacent to the gas discharge from said reverse turbine in cooperation with a circular flange-like projection extending generally radially inward from said casing opposite said peripheral groove, the edge of said peripheral groove which is nearest to said forward turbine joining the periphery of said shaft at a portion thereof which gradually reduces in diameter in the direction of said forward turbine, said peripheral groove and said circular projection jointly providing such a gas discharge flow path from said reverse turbine as to cause the discharge gases from said reverse turbine to flow initially in a centripetal direction toward the rotor axis and then turn gradually so as to flow in a centrifugal direction into said first passageway and thence out of said casing in a direction away from said forward turbine thereby preventing discharge gases from said reverse turbine from flowing along said first passageway in the direction of the blading of said forward turbine when said reverse turbine is being driven and similarly preventing discharge of gases from said forward turbine from flowing into said second passageway and through the blading of said reverse turbine when said forward turbine is being driven.

'2. A gas turbine for ship propulsion comprising a casing, a rotary shaft within said casing, stationary blading shaft, said stationary blading and said movable blading being cooperatively arranged to form a forward turbine and a reverse turbine axially spaced from each other, a first passageway extending longitudinally along the surface of said shaft in the direction of said reverse turbine and thence radially out of said casing for discharging gases from said forward turbine when said forward turbine only is being driven and a second passaageway for discharging gases from said reverse turbine into said first passageway when said reverse turbine only is being driven, said second passageway being constituted in part by a peripheral groove in a cylindrical deflecting member surrounding said shaft of arcuate cross section and normal.

to the shaft axis and disposed adjacent to the gas discharge from said reverse turbine in cooperation with a circular flange-like projection extending generally radially inward from said casing opposite said peripheral groove, said cylindrical member including a peripheral projection extending outwardly in parallel spaced relation to said circular projection, said peripheral groove and said circular and peripheral projections jointly providing such a gas discharge flow path from said reverse turbine as to cause the discharge gases from said reverse turbine to flow initially in a centripetal direction toward the rotor axis and then turn gradually so as to flow in a centrifugal direction into said first passageway and thence out of said casing in a direction away from said forward turbine thereby preventing discharge gases from said reverse turbine from flowing along said first passageway in the direction of the blading of said forward turbine when said reverse turbine is being driven and similarly preventing discharge of gases from said forward turbine fro-m flowing into said second passageway and through the blading of said reverse turbine when said forward turbine is being driven.

References Cited in the file of this patent UNITED STATES PATENTS 1,542,453 Hodgkinson June 16, 1925 1,802,329 Birmann Apr. 28, 1931 2,902,255 Huber Sept. 1, 1959 FOREIGN PATENTS 12,939A Great Britain June 22, 1905 398,128 France Mar. 15, 1909 519,058 Germany Feb. 23, 1931 OTHER REFERENCES Brown: Abstract of application Serial No. 135,943, published June 5, 1951, 647 0.6. 31-1. 

